Unit 11 Alcohols, Phenols And Ethers (Intext Questions-4)
Intext Questions
11.6 Give structures of the products you would expect when each of the following alcohol reacts with (a) $\mathrm{HCl}-\mathrm{ZnCl_2}$ (b) $\mathrm{HBr}$ and (c) $\mathrm{SOCl_2}$.
(i) Butan-1-ol
(ii) 2-Methylbutan-2-ol
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Answer
(a)
(i)
$\underset{\text{Butan-1-ol}}{\mathrm{CH_3}-\mathrm{CH_2}-\mathrm{CH_2}-\mathrm{CH_2}-\mathrm{OH}} \xrightarrow{\mathrm{HCl} \cdot \mathrm{ZnCl_2}} \text { No reaction }$
Primary alcohols do not react appreciably with Lucas’ reagent $\left(\mathrm{HCl}-\mathrm{ZnCl_2}\right)$ at room temperature.
(ii)
Tertiary alcohols react immediately with Lucas’ reagent
(b)
(i)
$\underset{\text{Butan-1-ol}}{\mathrm{CH_3} \mathrm{CH_2} \mathrm{CH_2} \mathrm{CH_2} \mathrm{OH}}+\mathrm{HBr} \xrightarrow{\mathrm{-H_2O}}\underset{\text{1-Bromobutane}}{\mathrm{CH_3} \mathrm{CH_2} \mathrm{CH_2} \mathrm{CH_2} \mathrm{Br}}$
(ii)
(c)
(i)
$\underset{\text{Butan-1-ol}}{\mathrm{CH_3} \mathrm{CH_2} \mathrm{CH_2} \mathrm{CH_2} \mathrm{OH}}\mathrm{SOCl_2} \longrightarrow \underset{\text{1-chlorobutane}}{\mathrm{CH_3} \mathrm{CH_2} \mathrm{CH_2} \mathrm{CH_2} \mathrm{Cl}}+\mathrm{SO_2}+\mathrm{HCl}$
(ii)
11.7 Predict the major product of acid catalysed dehydration of
(i) 1-methylcyclohexanol and
(ii) butan-1-ol
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Answer
(i)
(ii)
$\underset{\text{Butan-1-ol}}{\mathrm{CH_3} \mathrm{CH_2} \mathrm{CH_2} \mathrm{CH_2} \mathrm{OH}} \xrightarrow[\mathrm{H^+}]{\text { Dehydration }} \underset{\substack{\text{But-2-ene }\\ \text{(Major product)}}}{\mathrm{CH_3} \mathrm{CH}=\mathrm{CHCH_3}}+\mathrm{H_2} \mathrm{O}$
11.8 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.
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Answer
Resonance structure of the phenoxide ion
Resonance structures of $p$-nitrophenoxide ion
Resonance structures of o-nitrophenoxide ion
It can be observed that the presence of nitro groups increases the stability of phenoxide ion.
11.9 Write the equations involved in the following reactions:
(i) Reimer - Tiemann reaction
(ii) Kolbe’s reaction
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Answer
i. Reimer-Tiemann reaction
ii. Kolbe’s reaction
